LTC4068-4.2/LTC4068X-4.2
Standalone Linear
Li-Ion Battery Charger with
Programmable Termination
FEATURES
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DESCRIPTIO
Programmable Charge Current Up to 950mA
Complete Linear Charger in DFN Package
No MOSFET, Sense Resistor or Blocking Diode
Required
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
Charges Directly from a USB Port
Programmable Charge Current Termination
Preset 4.2V Charge Voltage with
±1%
Accuracy
Charge Current Monitor Output for Gas Gauging*
Automatic Recharge
Charge Status Output
“AC Present” Output
2.9V Trickle Charge Threshold (LTC4068)
Available Without Trickle Charge (LTC4068X)
Soft-Start Limits Inrush Current
Low Profile (3mm
×
3mm
×
0.75mm) DFN Package
The LTC
®
4068 is a complete constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its DFN package and low external component count make
the LTC4068 ideally suited for portable applications. Fur-
thermore, the LTC4068 is designed to work within USB
power specifications.
No external sense resistor or external blocking diode are
required due to the internal MOSFET architecture. Thermal
feedback regulates the charge current to limit the die
temperature during high power operation or high ambient
temperature conditions. The charge voltage is fixed at
4.2V and the charge current is programmed with a resis-
tor. The LTC4068 terminates the charge cycle when the
charge current drops below the programmed termination
threshold after the final float voltage is reached.
When the input supply (wall adapter or USB supply) is
removed, the LTC4068 enters a low current state dropping
the battery drain current to less than 2µA. Other features
include charge current monitor, undervoltage lockout,
automatic recharge and status pins to indicate charge
termination and the presence of adequate input voltage.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected by U.S. Patents, including 6522118.
APPLICATIO S
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Cellular Telephones, PDAs, MP3 Players
Bluetooth Applications
TYPICAL APPLICATIO
Complete Charge Cycle (750mAh Battery)
700
Single Cell Li-Ion Battery Charger with C/5 Termination
CHARGE CURRENT (mA)
600
500
400
300
200
100
CONSTANT
CURRENT
CONSTANT
VOLTAGE
600mA
V
IN
4.5V TO 6.5V
V
CC
BAT
LTC4068-4.2
CHRG
ACPR ITERM
EN
PROG
GND
+
825Ω
1.65k
1-CELL
Li-Ion
BATTERY
1µF
406842 TA01
0
3.00
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25
406842 TA02
TIME (HOURS)
406842fa
V
CC
= 5V
θ
JA
= 40°C/W
R
PROG
= 1.65k
R
TERM
= 825Ω
T
A
= 25°C
U
4.75
4.50
BATTERY VOLTAGE (V)
U
U
4.25
4.00
3.75
3.50
3.25
1
LTC4068-4.2/LTC4068X-4.2
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ITERM 1
BAT 2
CHRG 3
GND 4
9
8
7
6
5
EN
ACPR
V
CC
PROG
Input Supply Voltage (V
CC
) ....................... –0.3V to 10V
PROG, ITERM ................................ – 0.3V to V
CC
+ 0.3V
BAT ............................................................. –0.3V to 7V
CHRG, ACPR, EN ...................................... –0.3V to 10V
BAT Short-Circuit Duration .......................... Continuous
BAT Pin Current ........................................................ 1A
PROG Pin Current ................................................... 1mA
Maximum Junction Temperature .......................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
ORDER PART
NUMBER
LTC4068EDD-4.2
LTC4068XEDD-4.2
DD PART MARKING
LBHZ
LBQB
DD PACKAGE
8-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 40°C/W (NOTE 3)
EXPOSED PAD IS GROUND (PIN 9)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, unless otherwise noted.
SYMBOL
V
CC
I
CC
PARAMETER
Input Supply Voltage
Input Supply Current
Charge Mode (Note 4), R
PROG
= 10k
Standby Mode (Charge Terminated)
Shutdown Mode (EN = 5V, V
CC
< V
BAT
or V
CC
< V
UV
)
0°C
≤
T
A
≤
85°C, 4.3V < V
CC
< 6.5V
R
PROG
= 10k, Current Mode
R
PROG
= 2k, Current Mode
Standby Mode, V
BAT
= 4.2V
Shutdown Mode (EN = 5V, V
CC
< V
BAT
or
V
CC
< V
UV
)
Sleep Mode, V
CC
= 0V
V
BAT
< V
TRIKL
, R
PROG
= 2k (Note 5)
R
PROG
= 10k, V
BAT
Rising (Note 5)
R
PROG
= 10k (Note 5)
From V
CC
Low to High
●
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
●
●
●
●
MIN
4.25
TYP
0.4
200
25
MAX
6.5
1
500
50
4.242
105
535
–6
±2
±2
60
3
3.92
300
1
5
140
50
110
22.5
1.07
0.6
0.6
140
UNITS
V
mA
µA
µA
V
mA
mA
µA
µA
µA
mA
V
mV
V
mV
V
V
MΩ
mV
mV
mA
mA
V
V
V
mV
406842fa
V
FLOAT
I
BAT
Regulated Output (Float) Voltage
BAT Pin Current
4.158
92
465
4.2
100
500
–2.5
±1
±1
I
TRIKL
V
TRIKL
V
TRHYS
V
UV
V
UVHYS
V
EN(IL)
V
EN(IH)
R
EN
V
ASD
I
TERM
V
PROG
V
CHRG
V
ACPR
∆V
RECHRG
Trickle Charge Current
Trickle Charge Threshold Voltage
Trickle Charge Hysteresis Voltage
V
CC
Undervoltage Lockout Voltage
V
CC
Undervoltage Lockout Hysteresis
EN Pin Input Low Voltage
EN Pin Input High Voltage
EN Pin Pull-Down Resistor
V
CC
– V
BAT
Lockout Threshold
Charge Termination Current Threshold
PROG Pin Voltage
CHRG Pin Output Low Voltage
ACPR Pin Output Low Voltage
Recharge Battery Threshold Voltage
●
30
2.8
3.7
150
0.4
1.2
70
5
45
2.9
80
3.8
200
0.7
0.7
2
100
30
100
20
1
0.35
0.35
V
CC
from Low to High
V
CC
from High to Low
R
TERM
= 1k
R
TERM
= 5k
R
PROG
= 10k, Current Mode
I
CHRG
= 5mA
I
ACPR
= 5mA
V
FLOAT
– V
RECHRG
, 0°C
≤
T
A
≤
85°C
●
●
90
17.5
0.93
60
100
2
U
W
U
U
W W
W
LTC4068-4.2/LTC4068X-4.2
The
●
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, unless otherwise noted.
SYMBOL
T
LIM
R
ON
t
SS
t
RECHARGE
t
TERM
PARAMETER
Junction Temperature in Constant
Temperature Mode
Power FET “ON” Resistance
(Between V
CC
and BAT)
Soft-Start Time
Recharge Comparator Filter Time
Termination Comparator Filter Time
I
BAT
= 0 to I
BAT
=1000V/R
PROG
V
BAT
High to Low
I
BAT
Drops Below Charge Termination Threshold
0.75
400
CONDITIONS
MIN
TYP
120
600
100
2
1000
4.5
2500
MAX
UNITS
°C
mΩ
µs
ms
µs
ELECTRICAL CHARACTERISTICS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
The LTC4068E-4.2/LTC4068XE-4.2 are guaranteed to meet
performance specifications from 0°C to 70°C. Specifications over the
–40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 3:
Failure to solder the exposed backside of the package to the PC
board will result in a thermal resistance much higher than 40°C/W.
Note 4:
Supply current includes PROG pin current and ITERM pin current
(approximately 100µA each) but does not include any current delivered to
the battery through the BAT pin (approximately 100mA).
Note 5:
This parameter is not applicable to the LTC4068X.
TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage vs Supply
Voltage (Constant Current Mode)
1.015
1.010
1.005
V
CC
= 5V
V
BAT
= 4V
T
A
= 25°C
R
PROG
= 10k
V
PROG
(V)
V
PROG
(V)
1.000
0.995
1.0000
0.9975
0.9950
I
BAT
(mA)
0.990
0.985
4
4.5
5
5.5
V
CC
(V)
6
U W
6.5
7
405842 G01
PROG Pin Voltage
vs Temperature
1.0100
1.0075
1.0050
1.0025
400
300
200
100
0
Charge Current
vs PROG Pin Voltage
600
500
V
CC
= 5V
T
A
= 25°C
R
PROG
= 2k
R
TERM
= 2k
V
CC
= 5V
V
BAT
= 4V
R
PROG
= 10k
0.9925
0.9900
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
0
0.2
0.4
0.6
0.8
V
PROG
(V)
1
1.2
405842 G02
405842 G03
406842fa
3
LTC4068-4.2/LTC4068X-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
Regulated Output (Float) Voltage
vs Charge Current
4.26
V
CC
= 5V
4.24 T
A
= 25°C
R
PROG
= 1.25k
4.22
V
FLOAT
(V)
V
FLOAT
(V)
4.215
4.210
4.205
4.200
4.195
4.190
4.185
–50
4.18
4.16
4.14
4.12
4.10
0
100
200
300 400
I
BAT
(mA)
500
600
700
V
FLOAT
(V)
4.20
CHRG Pin I-V Curve
(Pull-Down State)
30
T
A
= –40°C
25
20
T
A
= 25°C
30
I
CHRG
(mA)
I
ACPR
(mA)
15
10
5
0
0
1
2
4
3
V
CHRG
(V)
5
V
CC
= 5V
V
BAT
= 4V
6
7
15
10
5
0
0
1
2
4
3
V
ACPR
(V)
5
6
7
I
TRKL
(mA)
T
A
= 90°C
Trickle Charge Current
vs Supply Voltage
60
50
R
PROG
= 2k
40
I
TRKL
(mA)
V
TRKL
(V)
30
20
10
0
R
PROG
= 10k
V
BAT
= 2.5V
T
A
= 25°C
LTC4068 ONLY
3.000
2.975
2.950
2.900
2.875
2.850
2.825
I
BAT
(mA)
4
4.5
5
5.5
V
CC
(V)
6
4
U W
405842 G04
405842 G07
Regulated Output (Float) Voltage
vs Temperature
V
CC
= 5V
R
PROG
= 10k
4.215
4.210
4.205
4.200
4.195
4.190
4.185
Regulated Output (Float) Voltage
vs Supply Voltage
T
A
= 25°C
R
PROG
= 10k
–25
0
25
50
TEMPERATURE (°C)
75
100
4
4.5
5
5.5
V
CC
(V)
6
6.5
7
405842 G05
405842 G06
ACPR Pin I-V Curve
(Pull-Down State)
60
T
A
= –40°C
25
20
T
A
= 25°C
Trickle Charge Current
vs Temperature
V
CC
= 5V
V
BAT
= 2.5V
LTC4068 ONLY
R
PROG
= 2k
T
A
= 90°C
50
40
30
20
10
0
–50
R
PROG
= 10k
V
CC
= 5V
V
BAT
= 4V
–25
0
25
50
TEMPERATURE (°C)
75
100
405842 G08
405842 G09
Trickle Charge Threshold Voltage
vs Temperature
V
CC
= 5V
R
PROG
= 10k
LTC4068 ONLY
600
500
400
300
200
100
Charge Current vs Battery Voltage
LTC4068 ONLY
2.925
6.5
7
2.800
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
0
2.4
V
CC
= 5V
θ
JA
= 40°C/W
R
PROG
= 2k
2.7
3
3.3 3.6
V
BAT
(V)
3.9
4.2
4.5
405842 G10
405842 G11
405842 G12
406842fa
LTC4068-4.2/LTC4068X-4.2
TYPICAL PERFOR A CE CHARACTERISTICS
Charge Current vs Supply Voltage
600
500
400
R
PROG
= 2k
500
R
PROG
= 2k
400
I
BAT
(mA)
I
BAT
(mA)
V
BAT
= 4V
300 T
A
= 25°C
θ
JA
= 40°C/W
200
100
0
R
PROG
= 10k
4
4.5
Power FET “ON” Resistance
vs Temperature
700
650
600
V
CC
= 4.2V
I
BAT
= 100mA
R
PROG
= 2k
R
DS(ON)
(mΩ)
550
500
450
400
350
–50
V
RECHRG
(V)
–25
PI FU CTIO S
ITERM (Pin 1):
Charge Termination Program. The charge
termination current threshold current is programmed by
connecting a 1% resistor, R
TERM
, to ground. The current
threshold I
TERM
, is set by the following formula:
voltage. This divider is disconnected in shutdown mode to
minimize current drain from the battery.
CHRG (Pin 3):
Charge Status Open-Drain Output. When
the battery is charging, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the charge cycle is
completed, CHRG becomes high impedance.
GND (Pins 4, 9):
Ground/Exposed Pad. The exposed
backside package pad (Pin 9) is electrical ground and
must be soldered to the PC board for maximum heat
transfer.
406842fa
I
TERM
=
100V
100V
, R
TERM
=
R
TERM
I
TERM
BAT (Pin 2):
Charge Current Output. Provides charge
current to the battery from the internal P-channel MOSFET,
and regulates the final float voltage to 4.2V. An internal
precision resistor divider from this pin sets the float
U W
5
Charge Current
vs Ambient Temperature
600
ONSET OF THERMAL REGULATION
300
200
100
0
–50
V
CC
= 5V
V
BAT
= 4V
θ
JA
= 40°C/W
R
PROG
= 10k
5.5
V
CC
(V)
6
6.5
7
–25
50
25
75
0
TEMPERATURE (°C)
100
125
405842 G13
405842 G14
Recharge Threshold Voltage
vs Temperature
4.16
4.14
4.12
4.10
4.08
4.06
4.04
–50
V
CC
= 5V
R
PROG
= 10k
0
25
50
75
TEMPERATURE (°C)
100
125
–25
0
25
50
TEMPERATURE (°C)
75
100
405842 G17
405842 G15
U
U
U
5
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